The baseband EPCN system refers to an Ethernet running on a coaxial network and adopts a point-to-multipoint coaxial distribution network as physical layer transmission medium. The coaxial distribution network may have, e.g. a star topology or a tree topology, etc.
The structure of the baseband EPCN system is shown in FIG. 1. A typical baseband EPCN system includes a Coax Line Terminal (CLT), a Coax Network Unit (CNU) and a coaxial distribution network, etc. The CLT is located in corridor or where a community optical node is located. The CNU is located where a user resides and functions as a Customer Premise Equipment (CPE) for access of a user terminal, or is integrated with products such as corridor switch to function as an uplink interface of the corridor switch. The coaxial distribution network is a network from a CATV optical node location to user's home. Besides coaxial cable, the coaxial distribution network further includes apparatuses such as active amplifier, branch/distributor, etc.
The baseband EPCN system mainly applied for user's broadband network access and video on demand, etc. These applications mainly request a high downlink bandwidth while have a low requirement for uplink bandwidth where the user residents. The baseband EPCN system is a time-division system based on physical channels. Accordingly, in a communication period, the system requires that an uplink period is longer than a downlink period in most situations, i.e., the downlink bandwidth is greater than the uplink bandwidth (e.g. 8:2). In a registration period, an un-registered CNU send a Register message to the CLT in the uplink period. The longer the uplink period, the more CNUs are allowed to register. Accordingly, average register time of a new CNU becomes shorter.
In a conventional baseband EPCN system, the proportion between the uplink bandwidth and the downlink bandwidth keeps unchanged in the registration period and the communication period. For example, the downlink always occupies 80% time-slots while the uplink always occupies 20% time-slots. As a result, it is impossible to satisfy requirements for both short register time and high downlink bandwidth at the same time. When the average register time of a new CNU is reduced, the downlink bandwidth in the communication period is reduced simultaneously. If the downlink bandwidth in the communication period is ensured, the average register time of the new CNU becomes longer in the registration period.